ACDC JIP

Status: Proposed

Offshore renewable energy is progressively moving to dynamic floating structures. It is desirable to place these floating structures in the harshest environments possible, in order to maximise power generation.

Power cables are composite structures of a number of different layers with discontinuous material properties. In dynamic applications, the movement of internal layers creates complex stress states with fatigue accumulating due to bending, axial, torsional and friction effects. Inter-layer relative movement results in additional damping and frictional stresses between wires.

In addition, in offshore floating renewable energy applications, waves and currents cause complex hydrodynamic loading of cables. In particular, Vortex-Induced Vibration (VIV) leads to high cycle, low stress fatigue damage. The amplitude of VIV response is known to be a function of he cable's constriction, which affects how much energy is dissipated by fraction between the different layers.

These conditions are inherently detrimental for the power cable, which is the critical link between the floating structure and the static sea bed.

The objective of the ACDC JIP is to dramatically improve the fundamental understanding of how power cables respond and accumulate fatigue-damage in dynamic floating renewable energy applications.

Over a number of work packages, the scope of the proposed ACDC JIP covers:

Both AC and DC cables

Both global and local numerical modelling

Large scale tank tests

Consideration of the influence of design parameters

Full scale field monitoring

The ACDC JIP aims to deliver a report with design guidance and practices to address the following questions:

How can a cable's design be improved to reduce inter-layer frictional stresses?

How much internal damping does the cable expereince under typical hydrodynamic and mechanical loading conditions?

Is there an optimum design point for multi-layered power cables and how can an optimum design be achieved?